Vodacom MyGig 5 Promo is a trap

I signed up to the MyGig 5 Promo though Vodacom on 06/07/2017 You sign up to this service, buy your own ****le and simply pay for data every month. Right? Wrong. I called them today to cancel my ****le. They stated that they cannot do this until my contract period is up or until 07/04/2019 which makes NO SENSE! I am paying for data monthly, I do not require that data any longer so I want to cancel the data going forward. They offered me a buy out clause of 2000 Rand which is essentially the price of the data I'd pay till 2019 (Contract expiry). I do not understand, I do not want the data anymore, I do not want to be charged for this data any more as I AM NEVER GOING TO USE IT. I also don't remember signing up for a fixed period. I want out.